Prospective Evaluation of Normal Supraspinatus Muscle Using Shear Wave Elastography: Comparison With Symptomatic Tendon Tears.

ABSTRACT

OBJECTIVE: This study aimed to evaluate normal supraspinatus (SS) muscle elasticity using shear wave elastography (SWE) in an asymptomatic group, analyze its correlation with demographic factors and ultrasound (US) grayscale grade, and compare the elasticity between normal SS muscles and symptomatic SS muscles with tendon tears. METHODS: A prospective study was conducted with 101 adult patients with normal SS muscle scheduled for surgery due to a contralateral shoulder with SS tendon tear. Both shoulders underwent US examinations, including SWE. The SWE values, including mean and median elasticity, as well as the elasticity ratio, were analyzed for their correlation with demographic characteristics and grayscale grades. A comparison of SWE values was performed between the normal and symptomatic SS muscle groups. RESULTS: The mean SWE modulus of the normal SS muscle was 27.87 kPa (±49.04), with an elasticity ratio of approximately 1.52 (±0.03). Males exhibited slightly higher elasticity ratios compared with females (1.61 vs 1.45, P = .016). The interobserver agreement for all SWE measurements was excellent (>0.8). Grayscale grade increased with age, showing a similar pattern in females (P < .001). However, no significant correlation was observed between SWE values and grayscale grade in the normal SS muscle group. SWE values in normal SS muscles were significantly lower than those with tendon tears (P < .001). CONCLUSIONS: SWE provides objective measurements of normal SS muscle elasticity. Gender-based variations were observed, with males exhibiting slightly higher elastography ratios. SWE values were significantly lower in asymptomatic SS muscles compared with those with tendon tears.